教你如何在SQL Server计算机列和平均值

以下为引用的内容：

SELECT    
Sales.Customer.CustomerID,    
Sales.SalesOrderHeader.SalesOrderID,    
SUM(Sales.SalesOrderDetail.LineTotal)
AS SubTotalFROM    
Sales.Customer    
INNER JOIN Sales.SalesOrderHeader    
ON Sales.SalesOrderHeader.Customer
ID=Sales.Customer.CustomerID    
INNER JOIN Sales.SalesOrderDetail    
ON Sales.SalesOrderDetail.SalesOrder
ID=Sales.SalesOrderHeader.SalesOrderIDGROUP BY    
Sales.Customer.CustomerID,    
Sales.SalesOrderHeader.SalesOrder
IDHAVING SUM(LineTotal) > 25000.00ORDER BY    
Sales.Customer.CustomerID,    
SalesOrderID ;

以下为引用的内容：

SELECT    
Sales.SalesOrderHeader.SalesOrderID,    
AVG(SUM(Sales.SalesOrderDetail.LineTotal))
AS AverageFROM    
Sales.SalesOrderHeader    
INNER JOIN Sales.SalesOrderDetail    
ON Sales.SalesOrderDetail.SalesOrder
ID=Sales.SalesOrderHeader.SalesOrder
IDGROUP BY    
Sales.SalesOrderHeader.SalesOrderID

以下为引用的内容：

Msg 130, Level 15, State 1, Line 1

Cannot perform an aggregate function on an expression

containing an aggregate or a subquery.

以下为引用的内容：

USE [AdventureWorks]
GO

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE FUNCTION [dbo].[SalesTotals_fnt]()
RETURNS TABLE
AS RETURN    
(SELECT SalesOrderID,
SUM(LineTotal)AS TotalSale    
FROM Sales.SalesOrderDetail    
GROUP BY Sales.SalesOrderDetail.SalesOrderID)

以下为引用的内容：

CREATE FUNCTION [dbo].[AverageSale_fns] (    
-- Add the parameters for the function here    
-- )RETURNS money
ASBEGIN    
-- Declare the return variable here    
DECLARE @Result money
-- Add the T-SQL statements to compute the return value here    
SET @Result=(SELECTAvg(TotalSale)AS AverageSale    
FROM dbo.SalesTotals_fnt())
-- Return the result of the function    
RETURN @Result
END

以下为引用的内容：

DECLARE @Avg moneySELECT @Avg=dbo.AverageSale_fns()
SELECT     *, @Avg as Average,    
TotalSale / @Avg as Ratio,     CASE        
WHEN TotalSale / @Avg > 1 THEN 'Above Average'      
WHEN TotalSale / @Avg < 1 THEN 'Below Average'        
ELSE 'Average'     END
FROM dbo.SalesTotals_fnt()